package com.ifeng.mu.util;

public class Distance {

	private static final float EARTH_RADIUS = 6378137;

	private static double rad(double d) {
		return (float) (d * Math.PI / 180.0);
	}

	public  double calDistance(double lng1, double lat1, double lag2, double lat2) {
		double radLat1 = rad(lat1);
		double radLat2 = rad(lat2);
		double a = radLat1 - radLat2;
		double b = rad(lng1) - rad(lag2);
		double s = (2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2)
				+ Math.cos(radLat1) * Math.cos(radLat2)
				* Math.pow(Math.sin(b / 2), 2))));
		s =  (s * EARTH_RADIUS);
		s = Math.round(s * 10000) / 10000;
		return s;
	}

	
	
	 public float calSpeed(double distance, long currentTime, long lastTime  )
	   {
		   float speed=0;
		   
		  float timeInterval= currentTime-lastTime;
		   if(timeInterval==0)
			   speed=0;
		   else
			   speed=(float)distance/(timeInterval/1000);
		   return speed;
		   
	   }
	
}